Oil/water separation in a novel cyclone separator

Abstract

Conventional bulk oil-water separation is performed in large gravity separators that take up large areas and potentially contain large volumes of hazardous material. An intensified bulk separator has the potential to provide significant benefit in saving space, especially where this is at a premium, and in improving safety. The I-SEP, a novel geometry of Axial-Flow Cyclone (also known as Uniflow or straight-through) separator, has been tested as an intensified bulk oil-water separator. The objective of this work is to quantify performance by producing a map of separation performance with variation of inlet conditions, using variation of outlet back pressure to make the separator adaptable to variable inlet flow. A second objective is to compare the experimental performance of the I-SEP with a mathematical model. Using a Perspex test-unit with kerosene, or a silicone-based oil, and water in a batch flow loop, a map has been produced for outlet compositions and separation efficiencies at multiple inlet velocities. This was done for a range of inlet water cuts from 10% to 90% and with a geometry varied by lengthening the separating chamber of the test unit. A Computational Fluid Dynamics model using the Reynolds-Stress model has been developed with the FLUENT 6.0 CFD code. This has been compared with quantitative flow visualisation data and drop sizing information to model the separation of the cyclone by a discrete-phase technique. An optimum configuration and operating conditions has been found, with peak efficiencies in excess of 80%. This shows the important effect in improving performance achieved by the manipulation of outlet flow splits using backpressure. This Axial-Flow Cyclone design achieves a broader range of separation effect than published Reverse-Flow Cyclone designs. However, the unit will need to undergo further development to reduce shear and maximise residence time at high swirl.